Those comments were echoed later by UN Syrian special envoy Staffan de Mistura, speaking to the UN Security Council, who said: "This is fine. But let's think about it - that is less than 2% [of the population]... we need much more."

There has been no movement from the Syrian government on the United Nation's appeal to allow the evacuation of some 700 critically injured and severely ill patients.

Russia, as one of the council's five permanent members, holds the power of veto on such resolutions.

"Gaining support for the resolution will not be easy - but we must try," Sweden said.

The Eastern Ghouta has been under siege since 2013. It is a strategically important area, lying on the outskirts of Syria's capital, Damascus - which can be hit by rockets fired by rebels in the nearby enclave.

It is completely surrounded by areas of Syrian government control - with the result that any aid delivery requires the approval of government forces.

But inside the Eastern Ghouta, the humanitarian situation is rapidly worsening.